LONDON, June 3: Sleeping on the job should possibly be regarded as good conduct rather than slacking, according to a new study conducted in the United States.

The research shows that napping for 30 minutes or an hour during the day maintains mental performance when the brain is overloaded. Without a “powernap” too much information flooding the brain of a busy employee can “fry” the neurons and lead to a loss of learning ability.

Daytime naps lasting an hour or less had previously been shown to improve alertness, productivity and mood, especially under sleep- deprived conditions such as those experienced by night-shift workers.

But it was not clear what effect napping had on the brain and whether it had an impact on learning.

US scientists at Harvard University in Cambridge, Massachusetts, asked 129 undergraduate students to carry out a series of visual discrimination tasks, in which letters and shapes on a screen had to be rapidly identified. Each test lasted about an hour and they were repeated four times a day in order deliberately to put the students under pressure.

With each successive session, volunteers needed increasingly longer learning times” to reliably identify targets.

But when students were allowed to nap between sessions the fall in performance was cancelled out or even reversed. A short nap between the second and third test sessions prevented the further deterioration normally seen in sessions three and four.

An hour-long nap at the same time reversed the deterioration seen in the second session.

The scientists, who reported their findings in the journal Nature Neuroscience, found that deep, slow-wave sleep (SWS) was important for enhancing performance.

Different versions of the experiment indicated that sleep, and not merely resting with the eyes closed, was necessary to produce the restorative effect. The researchers noted that powernaps were common among people experiencing daily information overload.

Students switched to a different visual input affecting a different part of the brain for the final test session showed a marked recovery in performance.

If general tiredness had been to blame, their performance would have been expected to continue deteriorating. The scientists, led by Sara Mednick, wrote: “It suggests that the psychological sensation of burnout’, described anecdotally as increased irritation and frustration along with decreased effectiveness after prolonged cognitive effort, may not reflect a general mental fatigue, but rather the specific need of an overused local neural network to enjoy the restorative benefits of sleep.”—dpa